The present invention relates to an antenna system for use in a wireless communication system; and, more particularly, to an antenna system incorporated therein an array of phase shifters for steering beams in three-dimensional.
As is well known, it is sometimes desirable to adjust the orientation of a radiation beam emitted from a broadcast antenna. In particular, if a broadcast antenna is installed at a higher altitude than other antennas that communicate with the broadcast antenna, it must be tilted downward to steering a radiation beam emitted therefrom. This down tilting of the radiation beam alters a coverage angle and may reduce interference with nearby broadcast antennas, and may enhance communications with mobile users situated in valleys below the broadcast antenna.
Referring to FIG. 1, there is shown a conventional antenna system 10, which is capable of mechanically down-tilting a beam 16 radiated from an antenna 12 incorporated into the antenna system 10. The antenna 12 is mounted atop a mast 14 at a height above ground which is in many cases about 200 feet.
In case when the orientation of a radiation beam is adjusted downward, the entire antenna 12 must be mechanically down tilted. One of the major shortcomings is that this approach is generally regarded as too rigid and too expensive. There is the approach that electrically down tilting the radiation beam by adjusting the relative phases of the radiation associated with each of several radiators of an antenna.
Referring to FIG. 2, there is shown a schematic diagram illustrating a conventional antenna system 20, which is capable of electrically down-tilting a beam 26 radiated from an antenna array 22 incorporated into the antenna system 20. In the system, the antenna array 22 incorporates therein an array of radiators and a single point signal feed network provided with a scan network to couple the single point network to the array 22 of radiators. The scan network includes a plurality of transmission lines between the feed network and each radiator. Among these electrical down tilting methods is a capacitive coupling method, in which an adjustable capacitance is placed in series with the transmission lines to provide a plurality of signals to each radiator of the antenna array 22, thus causing the desired phase shifts. A phase shifter is associated with each radiator of the antenna array 22 such that the phase shifted beam from each radiator constructively interferes with the beam 26 from every other radiator to produce a composite beam radiating at an angle from a line normal to the surface of the antenna. By changing the phase shift provided by each phase shifter, the beam can be scanned across the antenna surface. Another such approach is to use different lengths of transmission lines for feeding the different elements to produce a permanent electrical down tilting.
There are a number of problems associated with the above-described antenna systems 10, 20, however. First of all, both of the antenna systems 10, 20 cannot steer a radiation beam in horizontal direction.
Another problem of the prior art is that it requires a number of phase shifters corresponding to the number of the transmission lines in the prior art antenna systems 10, 20.
In addition, in the prior art antenna systems 10, 20, it requires a mechanically complex, for example using a rack and pinion assembly or a number of phase shifters corresponding to the number of radiators, for providing the desired phase shift.
Further, the prior art antenna systems 10, 20 cannot modulate a width of beam in horizontal and in vertical.
Finally, a beam is scanned in vertical and in horizontal by utilizing the prior art antenna systems, it has too much scan loss.
It is, therefore, an object of the present invention to provide an antenna array capable of electrically elevating a beam emitted therefrom by utilizing a multi-line phase shifter.
It is another abject of the present invention to provide an antenna system for electrically steering a beam emitted therefrom in horizontal by using a multi-line phase shifter.
It is another object of the present invention to provide an antenna system capable of electrically steering a beam radiated therefrom in both vertical and Azimuth direction.
It is another object of the present invention to provide an antenna system for selectively switching a beam width in horizontal by using a switchable divider.
It is another object of the present invention to provide an antenna system for controlling a beam radiated therefrom in a 3-way.
It is another object of the present invention to provide an antenna system for minimizing interference and maximizing cell capacity.
It is another object of the present invention to provide an antenna system for providing an optimal cell planning and meeting the real world of diverse environments.
It is another object of the present invention to provide an antenna system capable of harmonizing with communication environment.
It is another object of the present invention to provide an antenna system with a stable and stable installation.
In accordance with one aspect of the present invention, there is provided an antenna system for use in a wireless communication system, comprising: an array of Mxc3x97N radiating elements for emitting a beam, M and N being a positive integer, respectively; an input port for providing signals to the array of Mxc3x97N radiating elements; M number of first phase shifters for steering the beam on the basis of column by phase shifting the signals from the input port; N number of second phase shifters for steering the beam on the basis of row by phase shifting the signals; N number of switchable dividers for selectively transmitting the signals to a number of transmission lines incorporated into the second phase shifters; M number of combiner/dividers for transmitting the signals from the transmission lines of the second phase shifters to the transmission lines of the first phase shifters; a horizontal motor driver for control the first phase shifters; a vertical motor driver for control the second phase shifters; and a beam control board for control the horizontal motor driver, a vertical motor driver and the switchable dividers.
In accordance with another aspect of the present invention, there is provided an antenna system for use in a wireless communication system, comprising: an array of N radiating elements for emitting a beam, N being a positive integer; a feeding network for providing a plurality of signals to the array of N radiating elements; and a phase shifter for steering the beam by simultaneously phase shifting the signals from the feeding network.
In accordance with another aspect of the present invention, there is provided an antenna system for use in a wireless communication system, comprising: an array of N radiating elements for emitting a beam, N being a positive integer; a switchable divider for selectively providing a signal to the array of N radiating elements; and a phase shifter for steering the beam by simultaneously phase shifting the signals from the feeding network.